Jää-ajast Inglise keeles!
glaciers, were formed.
The edges of the sheets were pushed outward. At last the ice covered most of
what is now Canada. And it spread southward into what is now the United States.
The ice was probably a mile deep in places. It moved over hills and valleys,
rivers and forests. It moved slowly perhaps only a foot a day. Millions of plants
were buried by the ice. Many animals moved south. Among the animals able to stand
the cold near the edge of the ice were woolly mammoths, woolly rhinoceroses, and
caribou.
For thousands of years the ice moved southward. But at last the summers grew
longer and warmer, and the ice began to melt back. It melted back so that most of
North America was out from under it.
But again it grew colder and the ice sheets moved southward. Again it grew
warmer and they melted back. Twice more the ice moved slowly southward and twice
more it melted back.
During the great Ice Age much of Europe, too, was covered with ice
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